1. Field of the Invention
The present invention relates generally to roaming of a portable terminal in a Wireless Local Area Network (WLAN). More particularly, the present invention relates to a roaming method and apparatus for a WLAN requiring authentication for connecting to an Access Point (AP), wherein when a portable terminal in a standby mode is roaming between APs, the portable terminal is switched to an active mode for authentication.
2. Description of the Related Art
With increased popularity of wireless portable terminals, various efforts have been made to improve the performance and function of portable terminals. With advances in communication technologies, portable terminals support both voice calls and data calls based on packet switching for transmitting various data. Data call processing requiring relatively high power consumption has increased interest in power saving schemes for portable terminals with limited battery power.
A “Wake on WLAN” (WoW) mechanism, where a host or a control unit of a portable terminal is placed in a standby mode and is transitioned to an active mode only when needed, is one example of such power saving schemes.
When a portable terminal moves in a WLAN, roaming may have to be performed between Access Points (APs). More particularly, when connection to an access point requires authentication, a time delay may arise due to a search for a new AP and authentication requirements and data loss may occur during roaming. To overcome the problems of time delay and data loss, many schemes, such as roaming with pre-authentication have been proposed.
The WoW mechanism may cause a problem during roaming. As disclosed in the wireless network Institute of Electrical and Electronics Engineers (IEEE) 802.1x standard, the host or the control unit of a portable terminal performs signal transmission and reception while an authentication procedure is performed. Thus, if the control unit of the portable terminal is in standby mode when the authentication procedure is being performed, the authentication procedure may not be completed. Therefore, the network connection may be disrupted.
Therefore, a need exists for roaming method and apparatus for a portable terminal that maintains a network connection during roaming in a WLAN.